Vehicles such as automobiles are equipped with a transmission in order to convert driving force generated by the engine to a required form depending on the traveling state of such vehicle. There are various types of transmissions such as gear type, torque converter type and belt type. For example, in the belt type transmission, in order to convert engine driving force to a desired form by continuously varying the transmission gear ratio and taking off the same, the transmission, as shown in FIG. 10, is provided with an oil pump 102 driven by the engine (not shown), and a valve body 104 for regulating oil discharged by this oil pump 102 to a predetermined pressure level. The oil pump 102 is provided with an oil intake passage 112, a starting end of which communicates with the interior of an oil pan 106 and a terminating end of which communicates with an intake passage 110 of the oil pump 102 through a filter 108. An oil feed passage 116 has a starting end which communicates with a discharge passage 114 of the oil pump 102 and a terminating end which communicates with the valve body 104.
Owing to the foregoing arrangement, the valve body 104 feeds oil, which has been regulated to a predetermined pressure level, to a required return oil feed part of a transmission (not shown) and returns surplus oil, which is generated when the oil is regulated to the predetermined pressure level, to the oil pan 106.
However, since the oil feed passage 116 of the conventional transmission returns surplus return oil, which has already been filtered, this clean return oil is mixed in the oil pan 106 with oil which is not yet filtered. Furthermore, the oil pump is required to again pump this clean return oil through the filter 108.
Because of the foregoing, the filtered oil cannot be effectively utilized and the oil pump work becomes heavy, causing an undesirable increase in pump driving torque. Furthermore, because bubbles are generated in the clean oil returned from the valve body 104, there arise inconveniences such as deterioration of pumping efficiency and generation of noises. Moreover, because the clean return oil is caused to pass through the filter again, the quantity of oil passing through the filter becomes large. As a result, it is necessary to increase the filter area, causing the overall apparatus to be large.
Furthermore, since the oil feed passage 116 for feeding oil to the valve body 104 from the oil pump, and the oil return passage for returning the surplus clean return oil from the valve body, are separately provided, the total height of the transmission becomes high.
It is therefore an object of the present invention to provide an oil passage of a transmission which is capable of effectively utilizing filtered oil, reducing pump intaking work to diminish torque for driving the pump, preventing bubbling of return oil to enhance pump efficiency and to reduce noise, reducing the quantity of oil passing through the filter to attain a small size owing to reduced filter area, and lowering the total height of the transmission to enhance the strength of the transmission.
The present invention preferably includes a transmission having a transmission case comprising at least a first case portion and a second case portion. An oil pump is provided in said first case portion, a valve body being provided at said second case portion and adapted to regulate oil discharged by said oil pump to a predetermined pressure level, said oil pump being provided with a pump manifold, said manifold being provided with a filter adapted to filter oil stored in an oil pan beneath said transmission, an oil intake passage being provided in said pump manifold, a starting end of said oil intake passage being communicated with the interior of said oil pan and a terminating end thereof being communicated with said oil pump through said filter, said pump manifold being provided with an oil feed passage for feeding oil discharged by said oil pump to said valve body, and an oil return passage for returning surplus return oil from said valve body to said oil intake passage on the downstream side of said filter.
According to the preferred construction of the present invention, the pump manifold is provided with the oil feed passage for feeding oil discharged by the oil pump to the valve body and the oil return passage for returning surplus oil from the valve body to the oil intake passage on the downstream side of the filter. Accordingly, the filtered clean return oil can be prevented from being mixed with unfiltered oil, and the clean return oil does not pass through the filter again. Moreover, since the oil feed passage and the oil return passage are both disposed in the pump manifold, the total height of the transmission can be prevented from becoming high, as is caused by conventional separate provision of the oil feed passage and the oil return passage. The first and second case portions of the transmission can be connected with each other through the pump manifold which is provided with the oil feed passage and the oil return passage.